Fig. 1 Effect of grain refinement on dislocation density and hardness of AA1050 samples

Fig. 2 Optical micrograph of annealed AA1050 before severe plastic deformation method

Fig. 3 TEM micrograph and corresponding SAED pattern of UFG AA1050 sample

Fig. 4 Open-circuit potential a, potentiodynamic polarization b curves of CG, FG and UFG AA1050 samples in test solution (pH value of 8)

Fig. 5 Nyquist plots a, bode plots b of CG, FG and UFG AA1050 samples in test solution (pH value of 8)

Fig. 6 Kramers-Kronig transformation of the EIS data obtained for CG a, FG b, UFG c AA1050 samples in test solution (pH value of 8)

Fig. 7 Equivalent electrical circuit was proposed for modeling experimental EIS data

Fig. 8 Mott-Schottky plots of CG a, FG b, UFG c AA1050 samples in test solution (pH value of 8)

Fig. 9 Modified PDM for passivation of AA1050 in test solution (pH value of 8.0), where \(V_{\text{Al}}^{3 - }\) is aluminum vacancy on the aluminum sublattice of the passive film, \({\text{Al}}_{i}^{3 + }\) is interstitial aluminum, \({\text{Al}}_{\text{Al}}\) is aluminum cation on the aluminum sublattice of the passive film, \(V_{\text{O}}^{2 + }\) is oxygen vacancy on the oxygen sublattice of the passive film, \({\text{O}}_{\text{O}}\) is oxygen anion on the oxygen sublattice of the passive film, \({\text{Al}}^{3 + } \left( {\text{aq}} \right)\) is aluminum cation in solution